This straight transmission oils, without additives, has been formulated for use in conical torque, non-hypoid gear systems such as straight bevel, spiral bevel or worm gears.
The choice of viscosity is dictated by the technology used and the viscosity recommended by the manufacturer should be used.

As a general rule if the gear change is stiff when the gearbox is cold and becomes easier as it warms, due to the oil thinning during use, the correct grade oil is selected.

Transoil 250 is typically used in vehicles between 1918 & 1939.